BT will be able to supply millions of UK homes and businesses with broadband at speeds up to 8Mbps from the end of this month.

The telco announced on Thursday that faster broadband services will be available from 31 March. They are based on ADSL Max, which uses existing DSL standards with all rate limitations removed. This offers a much faster downlink speed than BT's current ADSL products, which have been rate limited since the service was launched.

However, while most broadband users should be able to get faster speeds than before, 8Mbps won't be universally available. Physical limitations mean that only 42 percent of phone lines will be able to support 6Mbps or faster, while 78 percent can get at least 4Mbps, according to information released by BT. Upstream speeds will reach 448kbps for consumer variants while an office version will reach 832kbps

For the full 8Mbps, BT says that people will have to be "living or working close to their local telephone exchange".

Many ISPs are expected to offer ADSL Max services, although only a few have published their plans so far. For example, Zen Internet will charge £24.99 per month for its 8Mbps consumer product, and £34.99 for the business version. Zen will upgrade its existing 2Mbps customers up to 8Mbps for free.

As BT Wholesale won't charge its ISP customers any more for 8Mbps products than it does for today's 2Mbps products, there's little reason for ISPs to raise their prices.

"It won't cost the service providers any more to regrade a line to 8Mbps, if they have already regraded it to 2Mbps in the past. If not, they have to pay £5 per customer," explained a BT Wholesale spokeswoman, adding that monthly charges and connection fees remain the same.

Some telecoms operators, such as UK Online, have been offering 8Mbps services in some urban locations since last year. BT, though, says it has taken longer because it wanted to make its service available to as many people as possible.